<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html lang="en">
<head>
	<meta http-equiv="Content-Type" content="text/html;charset=UTF-8">
	<title>Document</title>
	<style type="text/css">
	#box{
		margin-left:500px;
	}
    #nav{ 
      width: 150px;
      height: 60px;
      border: 1px solid red;
      background:#ccc;
      display: none;
    }
    </style>
    <script type="text/javascript">
    	window.onload = function () {
    		var Onav = document.getElementById("nav");
    		var Olabel = document.getElementsByTagName("label");
    		Olabel[0].onmouseover = function() {
    			Onav.style.display = "block"
    		};
    		Olabel[0].onmouseout = function() {
    			Onav.style.display = "none"
    		}

    	}
    </script>
   
	
	
</head>
<body>
<div id="box">
<label><input type="checkbox">两周内自动登录</label>
<div id="nav">为了您的信息安全，请不要在网吧或公用电脑上使用此功能！</div>
</div>	
</body>
</html>